Hydrocarbon is obtained from a subterranean formation by drilling a wellbore that penetrates the hydrocarbon-bearing formation. It is desirable to maximize both the rate of flow and the overall amount of flow of hydrocarbon from the subterranean formation to the surface.
The rate of hydrocarbon flow and the overall amount of hydrocarbon flow declines when the bottom hole flowing pressure falls below the dew point. When this occurs, a liquid aqueous phase accumulates near the well. This condensate accumulation, sometimes called condensate blocking, reduces the hydrocarbon relative permeability and thus the well's hydrocarbon productivity. In addition, the presence of aqueous liquids such as this condensate will cause the water swellable clays present in the formation to swell, which further reduces the formation's permeability. The productivity loss associated with condensate buildup can be substantial. In some cases, well productivities can decline by a factor of 2 to 4 as a result of condensate accumulation.
The rate of hydrocarbon flow and the overall amount of hydrocarbon flow can be impacted when well treatment fluids such as fracturing fluids, gravel pack fluids, and aqueous acidizing fluids are injected into the formation. Well treatment fluids sometimes decrease hydrocarbon's relative permeability through the formation compared to other fluids in the reservoir because of the limited reservoir pressure and capillary forces tightly holding the treatment fluids in the pore spaces previously occupied by hydrocarbon. The pockets of treatment fluid, which are interlocked with hydrocarbon, are hard to remove from the formation without some kind of stimulation treatment.
Another way that the rate of hydrocarbon flow and the overall amount of hydrocarbon flow can be reduced is by fines production or sand migration in the formation or by precipitation. The high velocity in the porous medium near the wellbore is sometimes sufficient to mobilize fines that can then plug channels in the formation. More often, formation sand and fines often become unstable and migrate as a result of water movement through the formation. Fines are most likely to move when the water phase is mobile because most formation fines are water-wet. The presence of a mobile water phase can cause fines migration and subsequent formation damage. It is desirable to minimize fines migration, since fines block flow paths, choking the potential production of the well, as well as causing damage to downhole and surface equipment, such as screens, pumps, flow lines, storage facilities, etc.
Hydrocarbon wells are often located in subterranean zones that contain unconsolidated particulates that may migrate within the subterranean formation with the oil, gas, water, and/or other fluids produced by the wells. Unconsolidated subterranean zones include those that contain loose particulates and those wherein the bonded particulates have insufficient bond strength to withstand the forces produced by the production of fluids through the zones.
Support devices such as screens and slotted liners are often used to provide support for these unconsolidated formations to inhibit formation collapse. In some instances, the annulus around the support device is gravel packed to reduce presence of voids between the device and the wellbore wall. Typically, such so-called “gravel packing operations” involve the pumping and placement of a quantity of a desired particulate into the unconsolidated formation in an area adjacent to a well bore. Gravel packing forms a filtration bed near the well bore that acts as a physical barrier to the transport of unconsolidated formation fines with the production of hydrocarbons. These support devices provide support for the wellbore and gravel packing and prevent some fines from entering the hydrocarbon flow into the well.
Some types of screens are adapted to be expanded to contact the wellbore wall either with or without gravel packing. It is however, impossible to eliminate all voids between the screen and the wellbore wall. Fines fill these voids blocking flow and in some instances fines flowing through these voids erode the screen destroying its effectiveness.
One common type of gravel packing operation involves placing a gravel pack screen in the well bore and packing the surrounding annulus between the screen and the well bore with gravel of a specific mesh size designed to prevent the passage of formation sand. The gravel pack screen is generally a filter assembly used to retain the gravel placed during gravel pack operation. A wide range of sizes and screen configurations are available to suit the characteristics of the gravel pack sand. Similarly, a wide range of gravel sizes is available to suit the characteristics of the unconsolidated or poorly consolidated particulates in the subterranean formation. The resulting structure presents a barrier to migrating sand from the formation while still permitting fluid flow.
Gravel packs may be time consuming and expensive to install. Due to the time and expense needed it is sometimes desirable to place a screen without the gravel and, particularly in cases in which an expandable screen is being placed, it may be unrealistic to place a bed of gravel between the expandable screen and the well bore. Even in circumstances in which it is practical to place a screen without a gravel pack, it is often difficult to determine an appropriate screen size to use as formation sands tend to have a wide distribution of sand grain sizes. When small quantities of sand are allowed to flow through a screen, screen erosion becomes a significant concern. As a result, the placement of gravel as well as the screen is often necessary to control the formation sands.
An expandable screen is often installed to maintain the diameter of the wellbore for ease of access at a later time by eliminating installation of conventional screens, gravel placement, and other equipment. However, the ability to provide universal screen mesh that can handle wide particle size distribution of formation sand is unrealistic, if not impossible.
Another method used to control particulates in unconsolidated formations involves consolidating a subterranean producing zone into hard, permeable masses. Consolidation of a subterranean formation zone often involves applying a resin followed by a spacer fluid and then a catalyst. Such resin application may be problematic when, for example, an insufficient amount of spacer fluid is used between the application of the resin and the application of the external catalyst. The resin may come into contact with the external catalyst in the well bore itself rather than in the unconsolidated subterranean producing zone. When resin is contacted with an external catalyst, an exothermic reaction occurs that may result in rapid polymerization, potentially damaging the formation by plugging the pore channels, halting pumping when the well bore is plugged with solid material, or resulting in a downhole explosion as a result of the heat of polymerization. Also, these conventional processes are not practical to treat long intervals of unconsolidated regions due to the difficulty in determining whether the entire interval has been successfully treated with both the resin and the external catalyst.
In addition to the unconsolidated formation sands often found in subterranean formations, particulate materials are often introduced into subterranean zones in conjunction with conductivity enhancing operations and sand control operations. Conductivity enhancing and sand control operations may be performed as individual treatments, or may be combined where desired.
While these unconsolidated formation treatment methods provide improved fines control, multiple treatment steps that are time consuming and expensive are required. Therefore, it is desirable to develop a relatively simple and relatively inexpensive treatment method and composition to improve or maintain the rate of hydrocarbon flow by reducing fines migration.